Dynamics of fluid flow inside carbon nanotubes

The dynamics of fluid flow through nanomachines is different from in other systems in that the flow is granular (no continuum assumption) and that the 'walls' move. We have performed molecular dynamics simulations of the flow of helium and argon inside carbon (graphite) nanotubes of several sizes. The fluid was started at some initial velocity; fluid particles were allowed to recycle axially through the tube via minimum image boundary conditions. Argon slowed down more quickly than helium. In addition, the behaviour of the fluid strongly depended on the rigidity of the tube; a dynamic tube slowed down the fluid far more quickly than one in which the tube was held frozen. It also depended on the fluid density and tube diameter. It did not, however, depend on the tube length, because fluid flow tended to prevent the development of strong longitudinal modes, whose behaviour is length dependent.